Firewood carries unwanted travelers: emerald ash borer

Delaware is surrounded by the emerald ash borer, an insect that can destroy a stand of mature ash trees in a matter of years.

It's in Pennsylvania, the western shore of Maryland and New Jersey, but so far, the insect hasn't been found in Delaware.

State officials are worried that people will accidentally bring the bugs into the state in hardwood firewood or on other wood products.

"That is exactly how emerald ash borer is being spread," said Jimmy Kroon, state survey coordinator with the cooperative agricultural pest survey.

Kroon said people can buy wood that is harvested locally or they can purchase wood that has a USDA seal that shows it has been heat-treated to kill off insects.

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Jimmy Kroon (left), state survey coordinator with the Delaware Department of Agriculture, is joined by Newark community affairs officer Ricky Nietubicz (center) and Newark's superintendent of Parks and Recreation as they examine an ash tree.(Photo: SUCHAT PEDERSON/THE NEWS JOURNAL)

In the meantime, state officials are monitoring wooded areas like in Newark's municipal parks to make sure the insect isn't here.

If the insects were to be discovered here, the impact could be significant in some subdivisions in north Wilmington. Ash trees were planted in northern Delaware as a replacement for elms when Dutch elm disease emerged. There are some neighborhoods with dozens of ash trees that are 50 to 60 years old.

The insect – about a half-inch long with an emerald green exoskeleton – doesn't cause the real problem. Instead, Kroon said, it is the larvae. Adult insects lay their eggs on the outside of tree bark.

Two to three weeks later, larvae hatch and begin to chew through the outer bark to the inner layer of tree bark. The larvae create a distinctive serpentine pattern in the soft, under bark structure that carries water and nutrients throughout the entire tree. The larvae spend the winter inside the tree bark. Then in May and June they emerge as adults, leaving D-shaped exit holes.

Kroon said the insects can kill a healthy tree in five years.

Adults will fly up to 3 miles a year to find ash trees. And when the insect was first discovered in a small grove of trees in Maryland, state officials went in and cut down all the ash trees within 2 miles to try to stop the insects before they took root, Kroon said.

But the insect spread anyway.

The insect was accidentally introduced from Asia in 2002 in southeast Michigan. Infestations have been found in 25 states: Arkansas, Colorado, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and Wisconsin. Since its discovery, it has killed millions of ash trees. Ash is one wood used to make baseball bats.

All 16 native ash species are susceptible to emerald ash borer. Sometimes, the only sign of a problem is when a homeowner starts to see dead branches near the top of a tree.

Other signs, according to the U.S. Department of Agriculture are leafy shoots rising from the trunk, spilling bark which exposes the serpentine channels formed by the feeding larvae, woodpeckers feeding on the trees and D-shaped holes where the larvae exit the tree.

In Delaware, state agriculture officials set monitoring traps in ash trees. The idea is to find adult insects before they can spread to healthy stands of trees.

So far, they haven't been spotted in the state.

But in Newark, Tom Zaleski, the city's park superintendent, is still worried.

He has a plan in place to treat the ash trees in municipal parks if the ash borer gets closer.

At some of the city's parks, you can hear the traffic of vehicles driving through on I-95. Zaleski believes that could be the route that the insects use to reach the city.

Once they are found within 20 miles of Newark, Zaleski said he plans to treat trees in an effort to protect them.

"We're been diversifying our urban forest canopy," he said. More types of trees build resistance to insects and disease.

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Jimmy Kroon (left), state survey coordinator with the Delaware Department of Agriculture, is joined by Newark community affairs officer Ricky Nietubicz (center) and Newark's superintendent of Parks and Recreation as he collects bug traps set up around the state looking for emerald ash borers.(Photo: SUCHAT PEDERSON/THE NEWS JOURNAL)

In an ash tree at Norma B. Handloff Park, Kroon has hung a purple triangular trap. It is baited with chemicals that mimic an ash tree in distress. That attracts ash borers if there are any nearby. The outside is covered with a sticky glue. Any insect that lands on the trap gets stuck.

Kroon uses a hook to remove the trap and checks each of the three sides. There is one insect that has a similar shape to the emerald ash borer so he removes it, places it in a vile and takes it back to his lab.

He checks another trap at Folk Memorial Park – this time a series of green cones. It, too, is baited with chemicals to attract emerald ash borers if they are nearby. Insects that fly into the trap are captured in a preservative solution.

He checks one more of the purple traps and removes another similar insect for closer inspection.

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Jimmy Kroon, state survey coordinator with the Delaware Department of Agriculture, takes one of the bugs from the bug trap to examine later under a microscope to see if it's the emerald ash borer.(Photo: SUCHAT PEDERSON/THE NEWS JOURNAL)

In the meantime, he checks a small, D-shaped hole in the bark of a tree. He scrapes away the bark for signs of ash borer larvae, but the tree is clean.

The two insects, it turned out, were not emerald ash borers.

Delaware is still insect-free, but no one can be certain how long that might last.

State officials urge residents and visitors to be careful with wood products and not bring in any from states where emerald ash borers are a known problem.